1. Field of the Invention
The invention relates to a method of automatically fabricating a dental superstructure, in particular an abutment possessing geometry for attachment to a dental implant. The superstructure may consist of one or more elements. In multi-element superstructures for attachment to dental implants, one element of the superstructure, namely the abutment, serves the biomechanical as well as the esthetic purpose of compensating for the angular difference between the axis of the implant and the occlusal direction in order to ensure that the masticatory forces are properly transferred to the implant in esthetically feasible solutions.
The purpose of an abutment is, among other things, to provide on its side oriented toward the jaw perfectly fitting means of attachment to the implant and to provide on its side oriented toward the oral cavity a structure that can be fitted with conventional prosthetics. In order to fulfill the second requirement in particular, the side of the abutment oriented toward the oral cavity has a post-like appearance. The post follows the axis of the tooth to be replaced. This axis is perpendicular to the occlusal surface of the teeth, especially in the case of molars.
2. Description of the Prior Art
The shapes of individual abutments have hitherto been determined by dental technicians or by the attending dentist.
Only standard abutments are used in prior art technology. Standard abutments having fixed tilt angles are available on the market for compensating the angle between the implant axis and the occlusion.
The procedure described in EP 1 062 916 A2 is based on inserting a so-called manipulation implant into a conventional cast and in this manner creating a situation in the model that simulates the situation in the patient's mouth after the implant has been introduced. This clinical set-up is then scanned for the purpose of producing an abutment and, if needed, an associated second element of the superstructure. An auxiliary device is used for scanning. With this procedure, the tasks that the dental technician must perform in prior art technology are simulated with the aid of a computer, ie, on the basis of a digitized 3D model, the necessary intermediate steps of modeling the abutment, the frame, and the veneer being performed in the computer in order to enable production of the final superstructure by means of a computer-controlled grinding machine. This is known as a CAD/CAM process.
Methods are disclosed in U.S. Pat. No. 5,989,029 and U.S. Pat. No. 6,231,342 for computation of a customized abutment from several scans carried out in different directions by modification of a standard abutment. With such methods, however, it is still necessary to make a dental impression.
It is an object of the invention to make it possible to design the shape of a customized abutment automatically within specific limits.
Determination of the compensating angle between the implant and the axis of the tooth, in addition to the outer design of the crown in relation to the occlusion, is critical for the proper functioning and esthetics of the superstructure.